Propeller control



June 11, 1946. MARTW 2,402,065

PROPELLER CONTROL Filed Nov. 5, 1942 4 Sheets-Sheet 1 INVENTOR 7739Mari??? di W f M flZ%r7zey June 11, 1946. E. MARTIN 2,402,065

PROPELLER' CONTROL Filed Nov. 5, 1942 4 Sheets-Sheet 5 Q: E INVENTORS E5 & Eriefiarizk t: E i BY Z Z June 11, 1946. E; MARTIN 2,402,065

PROPELLER CONTROL Filed NOV. 5, 1942 4 Sheets-Sheet 4 Q; L INVENTOR g L;Q Z7ZeMa?Z2'ii-. g E E mm 71% Patented June 11, 194

PBOPELLER CONTROL Eric Martin, West Hartford, Conn, assignor to UnitedAircraft Corporation, East Hartford, Comm, a corporation DelawareApplication November 5, 1942, Serial No. d64,621

' 27 Claims.

i; This invention relates to reversible propeller and a controltherefor, with particular reference to an improved feathering-typehydro-controllable propeller provided with reversing features and animproved control for operating the propeller in any of its various modesof operation.

An object of the invention is the provision of an improved propeller ofthe character indicated, including means for controlling the propellerpitch to maintain a substantially constant power plant speed, andpilot-controlled means for feathering. unfeathering and reversing thepropeller.

A further object is the provision of a propeller versing the propellerexcept when the propeller carrying airplane is on the ground.

Other objects and advantages will be apparent from the specification andclaims and from the accompanying drawings which illustrate what is nowconsidered to be a preferred embodiment of the invention.

In the drawings, Fig. 1 is a diagrammatic longitudinal sectional viewthrough a propeller hub constructed according to the invention.

Fig. 2'is a diagrammatic view showing the propeller hub and theconstant-speed control mean in section and dlagrammatically-illustratmgthe remainder of the control means in position to feather the propeller.

Fig. 3 is a view simila to Fig. 2 showing the control means in positionto unteather the propeller, and

Fig. 4 is a diagrammatic view similar to Figs. 2 and 3 showing thecontrol means in position to reverse the propeller.

Fig. 1 diagrammatically illustrates the principal elements of theimproved controllable-pitch reversing type propeller.

Such apropeller, as generally indicated at l0, may comprise a'hubportion I! mounted on a'propeller drive' shaft l4 and provided with aplurality of blade receiving sockets. such as the one indicated at 16.The propeller mayhave a plurality of blades mounted one in each socket,the blade for socket Hi being indicated at It. The blades are so mountedas to be rotatable about their longitudinal axes in pitch charmingdirections and may be retained in the sockets by suitable anti-frictionbearings, not

illustrated, interposed between a socket abut-- ment anda flange 20 onthe blade end in a manner well known to the art. Each blade is providedon its and within the hub member I2 with. a gear sector, as indicated at2! for blade 18, all of which gear sectors mesh with a master gear 22supported by the hub l2 and rotatable about the longitudinal axis of thehub. Gear 22,

is mounted upon a rotatable member 24 rotated through a cam and followermechanism, including movable cam rollers 26, 28 and fixed cam 3i, by apiston 30 reciprocable in a cylinder 32 connected to the front end ofhub l2 and having fluid connections to the opposite ends thereof as willpresently appear. The movable cam generally indicated at 33, has asubstantially straight intermediate portion 33a for constant-speedcontrol, a steep pitch portion 33b at the high pitch end for featheringthe propeller, and a steep pitch portion 330 at the low pitch end forreversing the propeller. The stationary cam 3! is similarly dethrough amember 44 which is an extension of shaft H. An annular piston 30, incylinder 32, has a tubular hub 56, mounted for reciprocation on shaftextension 44. Connection 38 leads through radial ports, and longitudinalchannels 46 in member 44, to the exterior of member 4A through ports 41between sealing rings 48 and so and ports 49 between ring 52 and 54. Thetubular hub 56 of piston 30 is also provided with a ring 01' ports 58through which fluid may pass. Fluid may also flow from channels 46 intothe rearward end of the cylinder 32 through one or more check valves 60arranged to open at a relatively. low oil pressure, for example on athirtyflve pound pressure differential between the fluid in channels 46and in the space between the piston and the rearward end of cylinder 32.Fluid at high pressure in the space rearward of the of cylinder 32through channel 62 and force 'piston 36 rearwardly, and fluid from thespace to the rear of the piston will be expelled through ports 58 andchannels 66 to connection as which will be vented to the governor pumpinlet. If the supply of oil to the front end of the cylinder. iscontinued, the piston will move rearwardly until ports 58 are covered byseal ring 50 (Fig, 3). whereupon fluid will be trapped in the space tothe rear of the piston and no further rearward movement of the pistoncan take place since the governor oil pressure is less than the fourhundred pounds per Square inch necessary to open check valve 62. Theclosure of port 58 by ring 56 thus constitutesa low pitch hydrauliclimit stop which definitely predetermines the mini:

mum pitch angle of the propeller blades as lon as the propeller isfunctioning under governor control. When fluid under pressure issuppliedthrough connections 38 and channels 66, as

shown in Fig. 2, the fluid will enter the space to the rear of thepiston through lowpressure valve 66 and force the piston forwardly,while fluid in the front end of the cylinder will flow out throughchannel 62 and connection 36 which will bevented to governor pump inlet66 by the governorat the same time that fluid under pressure is appliedto the connection 36. I

A high pitch limit stop for the governor controlled operation-of .thepropeller may be provided in any one of several ways known to the art,.for example, by chi-1181 8 the pitch of the cam which rotates the gear22, such a change in cam pitch being indicated at 66 in Fig. 1, therebyincreasing theresistance of the mechanism to further pitch change tosuch an extent that the resistance cannot 'be overcome by the hydraulicfluid at governor control pressure but may be overcome inorder toincrease the propeller pitch to a feathered condition by applyinghydraulic fluid at an increased pressure to the space at the rear of thepiston 36.

The propeller pitch changing mechanism,

therefore, operates between definite predeter mined lower and upperpitch limit stops as long asthe mechanism is supplied with fluid at a,pressure not exceeding a predetermined value used for constant speedcontrol by the governor 66. But the pitch may be moved beyond either ofthe cam 3 limit stops by the application of hydraulic fluid at a higherpressure sufficient to overcome the resistance of the change in thecampitch to feather the propeller; or to unseat check valve 62 toreverse the pitch, in a manner which will I6 meshing with a gear 66supported by a hollow axle in the governor base 62 to form a boosterpump. Hydraulic fluid, such as engine lubricating oil, may be suppliedto this pump from the engine lubricating oil system, which includes pump66 and relief valve 66. Oil from pump 66 flows through channel 66 tochamber ,66 from which it flows through check valve 62 to booster pumpintake 66. on through the booster pump flows through passage 66 to theannular channel 4 61 connected with the interior of the shaft 66 throughports in the shaft. A second annular channel 96, above the channel 61,and likewise connected with the interior of shaft 66, is also connectedthrough duct I66 with connection 36. Another annular channel I62, alsoconnected with the interior of shaft 66, is connected by duct I66withthe transfer bearing connection 36.

Within the upper; portion of hollow shaft 66 there is a hollow,vertically slidable, valve plunger I66 having spaced lands I66 and H6controlling the ports leading to annular channels 96 and I62respectively. At its upper end this plunger carr'ies an anti-frictioncollar II2 interposed between the arms of the flyballs I6 and the end ofthe speeder spring II6 so that the position of plunger I66 is determinedby the condition of balance between the rotatable flyballs and thespeeder spring. The loading on the speeder spring may be adjusted by aslidable abutment I I6 bearing against the upper end of the spring andpositioned by a pinion l I8 the teeth of which mesh with rack teeth onthe abutment, the pinion being rotated manually by lever I26 throughsheaves I26, I22 and cable I26.

Channel 61, in addition to being connected with pump outlet channel 66,is also connected with a relief valve I26 which regulates the pumpoutlet pressure by bypassing or venting some of the pump outlet fluidthrough channel I26 and the hollow axle of gear 66 to the fluid chamber66 whenever the pump outlet pressure exceeds the predetermined value forwhich the valve I26 is set.

The mechanism thus far described will provide for completeconstant-speed control of the propeller. In the case of an underspeedcondition of the propeller, flyballs I6 will move inwardly and springII6 will force plunger I66 downwardly until land I66 is below channel 66(Fig. 3), thus connecting channel 66 with the governor pump inlet 66through port I6l, the hollow interior of plunger I66, port I66, andchannels I36 and I32. At the same time land II6 will be moved below theports leading to channel I62 thereby connecting channel 61 with channelI62. Under these conditions fluid under pressure will be supplied to thepropeller through channel I66, connection 36 and channel 62 thus movingpiston 36 rearwardly to decrease the pitch. At the same time the spaceto the rear of piston 36 will be connected with governor pump inlet 66through channels 66, 61, 66, 36, I66, 66, I61, I66, I36 and I32.

If flyballs I6 move outwardly. due to an overspeed condition, plungerI66 will be lifted against the force of spring H6, and (as in Fig. 2)channel 66 will then be connected with channel 61 while channel I62 willbe connected through channel I36 with pump inlet 66. Under these- I62and I66. Switch point I is connected with one side of battery I66 theother side of which is connected with ground, as at I66. Connectingswitch point I40 with point I38 energizes solenoid I50 to move valveplunger I52 to open channel I64 to annular channel I84 and close of!drain channel I56 therefrom. Connection of terminal I88 with terminalI42 energizes solenoid I58 surrounding an armature connected to buttonI34 to maintain the button in depressed condition as long as the batterycircuit is not interrupted. The opposite side of solenoid I58 isconnected through conduit I80 with a pressure actuated switch I62 theopposite side of which is connected with ground, as indicated at I64, sothat opening and closing of switch I82 will controlthe energization ofsolenoid I58. Connection of terminal I38 with terminal I44 energizessolenoid I66 of the relay which operates switch I68 controllingenergization of motor I which motor drives high pressure pump I12.

Pump I12 draws fluid from reservoir I18 and delivers it through conduit16 to pressure ohan-,

nel 81. A. check valve I18 is interposed in channel I16 so that pressurefluid from the governor booster pump will not feed back through the lineI18 when pump I12 is not operating. High pressure fluid from pump I12 isalso prevented from feeding back through the governor booster pump andreliefvalve 86 by check valve 92 interposed in the intake line 94 of thegovernor booster pump. Some of the pressure fluid from the line I16 isled through channel I80 and slide valve I82 to the space behind reliefvalve I28 50 that this valve cannot act to relieve pressure in channel91, and other fluid is led from line I16 through channel I54 and valveI52 to an annular channel I84 connected with the interior of shaft 88below plunger I06, the lower end of which is closed and forms a pistonI86, thus forming a chamber I80 in shaft 56 immediately below theplunger so that fluid introduced into the chamber from channel I84 willraise Plunger I08 and maintain it in raised position, connecting channel98 with channel 81, and channel I02 with channel I30 leading to thegovernor pump intake 90. Under these conditions fluid under pressurewill be supplied to the propeller through channel I00, connection 88,channel 48 and check valve 60 to move piston 30 forwardly, therebyincreasing the propeller pitch. As the output of pump I12 is of asufii-r ciently high pressure to overcome the high pitch limit stop 84(Fig. 1) pump I12 will continue to operate until the propeller hasreached its limiting high pitch or full-feathered condition. When piston80 reaches the end of its stroke in a pitch increasing direction (Fig.2), a pressure surge will occur in th fluid being supplied to cylinder82 which pressure surge is communicated through channels 88, I00, 98,91, 96 and HI to the pressure actuated switch I82, causin it tointerrupt the current through solenoid I58 thereby permitting spring I92to move contactor 86 to an open circuit position. Thereupon theoperation or pump I12 will cease and the valve plunger I52 will returnto the position in which it closes channel I54 and opens drain channelI66 thus venting chamber I88 and restoring con trol of plunger I08 toflyballs 14 and speederspring I I4 while leaving the propeller in itsfeathered condition.

None of the drawings illustrate the port in position for constant speedoperation. Figs. 2, 3 and 4 all show conditions in which thefeatherpermits pressure from passage I00 to move valve 1 I-82 to theleft, thus connecting channel I00 with high pressure relief valve 24 andunloading the valve I28 so that the latter can be backed up by thepressure existing in channel I00. Valve I28 opens at comparatively lowpressure, therefore, in order to insure completion of the feathering,unfeathering and reversing operations it is necessary that it be backedup by pressure from pump I12.

7 In order to unfeather the propeller the governor control handle I28 ismoved to the extreme low speed position, illustrated in Fig. 3 in whichposition the terminals of the switch 2I4 are brought into contact.Button zit is then oepressed, as also shown in Fig. 3, moving contactorm to interconnect switch terminals 220 and 222. Terminal 220 isconnected with one side of battery I48, and terminal 222 is connectedwith relay solenoid I88 which operates contactor I88 controlling theenergization of motor I10 of high pressure pump I12. The electricconduit from terminal 222 to solenoid I68 leads through switch 2I4 sothat pump I12 cannot be operated to unfeather the propeller unless thegovernor speed control lever is in the low speed position indicated inFig. 3.

Since the propeller does not rotate when in its feathered conditionshaft 88 and flyballs 14 will not be rotating when the unfeatheringoperation is initiated and spring II4 will consequently hold plunger I06 in its lowermost position even though control lever I28 is moved to aposition unloading spring II4 for low speed governor operation. Theoutput of pump I12 will then flow through channel I16 and check valveI18 to pressure channel 91 and along plunger I08 to channel I02 fromwhich it will be delivered through conduit I04, connection 36 andchannel 42 to the front end of cylinder 32 to move piston 80 in a pitchdecreasing direction, fluid at the rear of the piston passing throughcheck valve 62.

As the propeller blades move out of their feathered condition thepropeller will start to turn and will rotate governor shaft 66. As soonas the propeller speed comes up to the 10w speed setting of thegovernor, fiyballs 14 will start to move the plunger I08 and thegovernor will take over control of the propeller pitch. If button 2I6 ismaintained depressed after the governor control has been reestablishedthe only effect will be that the governor will operate the propellerwith the high pressure oil from pump I12. As long as pump I12 is inoperation the governor booster pump will build up a pressure equal tothat produced in the governor lines by pump I12 since relief valve I28will not be able to relieve the outletpressure of the governor pump.

While maintaining button 2l6 depressed will not do any particular harmafter the propeller starts to rotate, the pilot may watch his enginetachometer and release the button as soon as rotation of the propellerhas been well established, as otherwise there will be an unnecessarywasteof energy of battery I46, and an unneces- ,ing pump I12 isdelivering oil through conduit I16. Oil flowing through that conduitenters passage I80 and acts on slide valve I82 to move sary period ofsubjecting the propeller and governor mechanism to high pressure fluidfrom pump I12. When button 2I6 is released spring 224 will movecontactor 2I8 to a position disconnecting terminals 2 20'and 222 andthereby deenergizingthe pump motor I10. A soon as pump I12 ceases tooperate, check valve I18 will close of! line I18 and slide valve I82will be moved to the left in order to return control to the governorbooster pump thereby reducing the pressure of the fluid in the governorand propeller. v

The reversing operation is particularly illustrated in Fig. 4. This isaccomplished by depressing button 228 causing contactor 228 to connectswitch terminals 238, 232 and 234. Terminal 232 is connected withsolenoid 238 which maintains button 228 depressed against the force ofspring determine the full reverse pitch or the propeller.

' engine throttle retarded before the reversing op- 238, and theconnection from the opposite end of the solenoid leads through pressureactuated switch I82 to ground I84 so that solenoid 238 may bedeenergized upon actuation of switch I82. Terminal 234 leads to relaysolenoid I88, controlling switch I88 of motor I18 through a switch 248carried by the landing gear and so arranged -that its elements are incontact only when the landing gear is lowered to landing position andloaded by the weight of the airplane. Thus motor I18 cannot be operatedto reverse the propeller while the airplane Is in flight.

In the case of a seaplane switch'248 may be some form of hydrostaticswitch closed only when the seaplane is on the water.

With button 228 depressed and switch 248 closed motor I18 will drivepump I12 to deliver fluid under high pressure through conduit I18 andcheck valve I18 to pressure channel 81. However, before the propellercan be reversed the manual control lever I28 for setting the governormust be moved to the high speed position indicated in Fig. 4 in order tocompress spring I I4 to move plunger I88 downwardly, and the enginethrottle must be retarded to a position at which eration is initiated,the propeller will be in its limiting low pitch condition when thereversing operation is begun so that the operation actually starts withports 58 covered by ring 58. As the piston 38 moves rearwardly from thisposition and passes relief port 48 and comes to a position in which port58 is covered by ring 84 a pressure surge will be established in thefluid between pump I12 and the propeller, which will operate throughchannel I8I to open switch I82 to demergize solenoid 238, therebypermitting button 228 to move outwardly under the force of spring 288 tomove contactor 228 to disconnect terminals 238. 282 and 234 therebydiscontinuing operation of pump I12 with the propeller in reverse pitch.

The propeller may be gotten out of the reverse pitch condition by movinggovernor speed control lever I28 to a low governor speedposition andthen opening the engine throttle sufliciently to create a suflicientflyball force to move plunger I88 to connect channel 81 with channel 88,and connect channel I82 with drain channel I38.

Asafety valve 243 is connected with the space at the back of reliefvalve I28 in order to permit fiyballs 14 do not exert sufficient forceto overcome the force of the spring and raise the plunger. If desired,an additional safety feature may be incorporated by placing a switch onthe engine throttle in series with switch 248 so that motor I18 cannotbe operated to reverse the propeller unless the throttle is retardedpast a predetermined setting.

With plunger I88 held in its lowermost position, as indicated above,high pressure fluid from channel 81 will flow to channel I82 and thencethrough channel I84 to transfer bearing connection 38 and then throughpropeller channel 42 to the. front end of cylinder 32 to move piston 38rearwardly in a pitch decreasing direction. The piston will move easilyas long as Ports 88 are uncovered but, when the piston has movedrearwardly until these ports are covered by the ring 88, fluid will betrapped in the cylinder space at.

the rear of the piston, and the hydraulic low pitch limit stop willbecome effective to resist further decrease in the propellerpitch. Sincepump I12 produces a pressure greater than that necessary to open checkvalve 82, continued operation of the pump will open this valve andpermit the fluid trapped in the rear cylinder space to exhaust throughvalve 82 thus permitting piston 38 to override the low pitch limit stop.Once the ports have passed ring 58, however, the fluid trapped in the.rearward cylinder space will be vented through auxiliary channels 48leading to channels 48 and the resistance imposed by the valve in theport 82 will be removed. Under these conditions, pump motor switch I88 iclosed, check valve I18 is open and'the slide valve I82 is in its righthand position to apply the fluid assure at the outlet of pump I12 to therear of reflex valve I28.

A positive low pitch limit stop is provided to valve I28 to open andrelieve the pressure produced by either of the pumps if such pumppressure tends to exceed a predetermined safe limiting value.

Oil reservoir I14 contains an auxiliary tank I88 through which oilcirculates rapidly in order to alway have available, (under normaloperating conditions) a supply of warm, free flowing oil for suchoperations as feathering the propeller. Oil returning through enginedrain 288 lands on a saucer 284 within reservoir I14 and spills over therim thereof into tank I88. Within tank I88 is a hopper 288 into which011 overflows at 288.

Engine lubricating oil is drawn by pump 84 through pipe 282 the, suctionend of which is connected to sump 2I8, into which oil feeds directlyfrom hopper 288, and indirectly from main reservoir I14 from which 011enters the sump around the lower end of the hopper.

Oil for feathering the propeller is drawn by pump, I12 through suctionpipe I84 connected to th bottom of auxiliary tank I88, therefore alwaysdrawing warm oil just returned from the 'engine lubricating system. Acheck'valve 2I2 allows warm oil to flow automatically from hopper 288into tank I88 if additional warm oil is needed therein. I,

It is to be understood that the invention is not limited to the specificembodiment herein illustrated and described, but may be used in otherways without departure from its spirit as defined tor is operated byfluid at pressures within said predetermined pressure range, meansrendering said limit stop ineffective to limit the pitch applied to saidmotor, manually operable means controlling said high pressure fluidsupply means for applying to said propeller fluid at a pressuresuflicient to render said limit stop ineffective and operate said motorto decrease the propeller pitch below said lowpitch limit stop, apositive 'low pitch limit stop effective to terminate the pitchdecreasing operation of said motor, and

means, actuated upon the termination of motor 'foperation andoperatively connected with said high pressure fluid supply means, fordiscontinuing the operation of said high pressure fluid supply meanswhen the propeller pitch is reduced to an angle determined by said lowpitch limit stop, 2. In the combination of a controllable-pitchpropeller having a hydraulic pitch changing motor and a propellercontrol including a speeclgovemor, means for supplying hydraulicfluid'at pres governor control of said propeller, and means forsupplying fluid at pressures above said predetermined pressure range forfeathering, unfeathering and reversing said propeller, a releasablelimit stop restraining said motor against changing the propeller pitchbelow a predetermined pitch angle while said motor is operated by fluidat pressures within said predetermined pressure range,

means rendering said limit stop ineffective to.

limit the pitch changing movements of said motorwhen fluid at a pressureabove said predetermined range is applied to said motor, manuallyoperable means for controlling said high pressure fluid supply means forapplying to said propeller fluid at a pressure sumcient to render saidlimit stop ineffective to limit the pitch changing movements of saidmotor and decrease the propeller pitch below said low pitch limit stop,an

' airplane landing gear, and means carried by said landing gear andoperatively connected with said high pressure fluid supply means toprevent operation of said high pressure fluid supply means j forgovernor "controlled operation of said pro- -sures within apredetermined pressure range for peller, and an electric motor drivenpump for, w

supplying hydraulic fluid to said motor at pressures above saidpredetermined pressure range for feathering, unfeathering and reversingsaid propeller, a releasable limit stop operatively associated with saidmotor for restraining said motor against changing the propeller pitchbelow a predetermined pitch angle while said motor is operated by fluidat pressures within said predetermined pressure range, means renderingsaid limit stop ineffective to limit the pitch changing movements ofsaid motor when motor operating fluid at a pressure above saidpredetermined pressure range is applied to said motor, a manuallyoperable switch operatively connected with said electric motor drivenpump to control the operation thereof, a spring urging said switch toopen position, a solenoid acting against the force of said spring whenenergized to maintain said switch closed, and a pressure switch subjectto the pressure of the fluid supplied to said motor and connected inseries with said solenoid to deenergize said solenoid when said motorreaches the end of its pitch reducing stroke.

4. The "arrangement cluding an airplane landing gear and a switchmounted on said landing gearand connected in series between saidmanually operable switch and said motor driven pump to prevent actuationof said pump by said manually operable switch except when said landinggear is extended an loaded.

5. In combination with a controllable-pitch propeller having a hydraulicpitch changing motor and means for supplying high pressure fluid to saidmotor to turn the propeller blades to a reverse pitch position, a fluidconnection between said fluid supply means and said motor, a speedgovernor, and a valve operated by said governor and interposed in saidfluid connection to render said motor ineffective to turn the propellerblades to a reverse pitch position except when the rotational speed ofsaid propeller is below the speed setting of said governor.

6. In combination, a propeller, a hydraulic double acting propellerpitch changing motor therefor, a first source of fluid under pressure, a

speed responsive governo'r actuated valve control-- ling the applicationof said fluid to said motor, stops limiting the extent of movement ofsaid motor under the influence of said fluid, a second source of fluidunder pressure higher than said firstfluid pressure, means leading fluidat said higher pressure to said governor actuated valve, manuallycontrolled means for moving said valve to direct said higher fluidpressure to either selected side of said motor to render the respectivelimit stop ineffective and either feather or reverse said propeller,said valve moving means comprising mechanism for directing fluid to oneend of said valve for moving it in one direction and mechanism forcompressing the governor spring to move the valve in the otherdirection.

7. In combination, a double acting fluid actuated propeller pitchchanging motor, a source of fluid under'pressure, a valve, speedresponsive means actuating said valve to'selectively direct said fluidunder pressure to either side of said motor, manually controlled means,including mechanism for selecting the governor speed setting, for movingsaid valve to one extreme position, a second manually controlledmeans'for energizing a source of fluid at a higher pressure, conduitsleading to said fluid at said higher pressure to said valve, and meanscontrolled by said valve moving means for preventing energization ofsaid source .of fluid at said higher pressure by said second manuallycontrolled means except when said speed selecting means is in its lowspeed position.

8. In combination, a fluid actuated propeller V pitch changing motor, asource of fluid-under pressure, a governor controlled valve fordirecting said fluid under pressure to said motor, a piston operativelyconnected with said valve, an-

other valve having a fluid connection with said piston, a drainconnection, manually controlled means for substantially simultaneouslyapplying fluid at a higher pressure to said overnor conas set forth inclaim 3 inl1 pressure, a relief valve for controlling the pressure ofsaid fluid, a governor controlled valve for directing said fluid underpressure to said motor,

a source of fluid, at a higher pressure, a relief valve set for apressure higher than said first mentioned relief valve, 9. pistonoperatively connected with said overnor controlling valve, another valvehaving a fluid connection with said piston, a drain connection, manuallycontrolled means for substantially simultaneously applying fluid at saidhigher pressure to said governor controlled valve and moving saidgovernor controlled valve to an extreme position to connect said higherpressure fluid to a selected side of said motor, including means for.moving said another valve to nnect said piston irom said drainconnection and connect said piston with said higher pressure fluid tothereby move said governor valve-to its extreme position includingmeansfor rendering said first mentioned relief valve inoperative andconnecting in said relief valve set for a higher pressure.

- 10. In combination with a fluid actuated motor, fluid supply meansconnected to said motor for supplying fluid under pressure thereto, apressure relief valve connected with said supply means -for limiting thepressure developed by said sup:

ply means, a governor actuated valve interposed between said fluidsupply means and said motor controlling the application of said fluid tosaid motor, and manually controlled means for rendaring said governoractuated valve ineil'ective and applying hydraulic fluid to said motoruntil it reaches a limiting position, said manually controlled meansincluding, a pump tor supplying fluid at a high pressure above theoutput pressure of said fluid supply means, means actuated by said highpressure fluid to maintain said relief valve closed, and means actuatedby said high pressure fluid for maintaining said governor actuated valvein a limiting position in which it maintains an open connection betweenone side of said motor'and said pump and an open drain ice. from theopposite side of said motor.

11. In combination with a fluid actuated motor, a first pump forapplying fluid under pressure to said motor, a relief valve for saidpump,

14. In e. propeller pitch control, a double acting hydraulic pitchchanging motor, a pump for supplying fluid under pressure, two fluidpressure lines; one leading to one side of said motor and the otherleading to the other side of said motor, a speed-governor-actuated valveselectively connecting said pump with one or the other of said lines, apressure relief valve connected with said pump for controlling thepressure developed by said pump, resilient means urging said valve toclosed position, a channel connecting the rear of said relief valve withsaid one pressure line whereby the fluid pressure in said one pressureline assists said resilient means in urging said valve to closedposition.

15. In 9, propeller pitch control, a double acting hydraulic pitchchanging motor, a first pump for supplying fluid under pressure, abooster pump for boosting the pressure developed by said first pump, twofluid pressure lines, one leading to one side of said motor and theother leadin to the other side of said motor, a speed governor actuatedvalve selectively connecting said first pump with said one line and saidbooster pump with said other line or reversing the connections betweensaid pumps and'said lines, a pressure relieivalve connected with saidbooster pump for controlling the pressure developed by said boostorpump, resilient means urging said valve to closed position, a channelconnecting the rear of said relief valve with said one pressure linewhereby the fluid pressure in said one pressure line assists saidresilient means in urging said valve to closed position.

v 16. In a control for a hydro-controllable propeller, a hydraulic pitchchanging motor, a pump for supplying fluid under pressure, a fluidconnection between said pump and saidmotor, a

a governor actuated valve for controlling the application of said fluidto said motor, and menually controlled means for operating said motorcomprising, a second pump delivering fluid at a pressure above thepressure setting of said relief valve, means operated by the fluidpressure from said second pump maintaining said reliervalve closed,means operated by the fluid pressure from said second pump maintainingsaid governor ac. .tuated valve in a limiting position in which itmaintains an open connection between theoutlets of said pumps and oneend of said motor and an open drain connection from the opposite end ofsaid motor, and a high pressure safety valve connected with the outletsof said pumps. 12. The invention set forth in claim 13 in which saidpreventing means is under control of the airplane pilot.

18. A control for a feathering and uni'eatherlug propeller comprising,means for regulating the speed of said propeller including a governorhaving a range of speed settings and having a low'speed setting at oneend of said range energizablemeans for unfeathering said propeller andmeans controlled by said speed regulating means for preventingenergization-of said unfeathering means except when said governor is setin its low spoedsetting. 7

speed governor, a valve, actuated by said governor, intercepting said,connection, and operative to connect said motor with said pump or with avent, a pressure relief valve for said pump, a first fluid channelconnecting said reliefvalve with the portion or said fluid connectionbetween said governor operated valve and said pitch changing motor toappl the pressureentering or leavin said motor to said relief valve tourge said relief valve to closed position, resilient means urging saidrelief valve to closed position, a valve in said channel urged by thepressure of fluid in said fluid connection to a position to maintainsaid channel open, and means for moving said lastmentioned valve toanother position to block said channel and modify the action of saidrelief valve.

. 17. In a control for a hydro-controllable propeller, a hydraulic pitchchanging motor, a pump for supplying fluid underpressure, a fluidconnection between said pump and said motor, a speed governor, a valveactuated by said governor, intercepting saidconnection, andoperative toconnect said motor with said pump or with a vent, a pressure reliefvalve for said pump. a first fluid channel connecting said relief valvewith the portion of said fluid connection between said governo operatedvalve and said pitch chrnging motor to apply the pressure entering orleaving said motor to said relief valve to urge said "uthepressureotfluidinsaidflrstfluidconnectioo supplying fluid underpressure, abooster pump,

for boosting the pressure developed by said first pump, two fluidpressure lines, one leading to one side of said motor and the otherleading to the other side of said motor, a speed governor actuated valveselectively connecting said first pump with said one line and saidbooster pump with said other line or reversing the connections betweensaid pumps and said lines, a pressure relief valve connected with saidbooster pump for controlling the pressure developed by said boosterpump, resilient means urging said valve to closed position, a channelconnecting the rear of said relief valve with said one pressure linewhereby the fluid pressure in said one pressure line assists saidresilient means in urging aid valve to closed position, a slide valve insaid channel urged by the pressure in said pressure line to a positionto 21. A device as claimed in claim in which said second source of fluidunderpressure is electrically controlled and said mechanism fordirecting fluid to said piston includes an electrically controlledvalve.

22. A device as claimed in claim 20in which said second source of fluidunder pressure comprises an electricallydriven pump and saidmechmaintain said channel open, a third pump for supplying fluid underpressure, means connecting the outlet of said third pump with the outletof said booster pump, a second channel interrupted by said slide valveand connecting the outlet of said third pump with the rear of saidrelief valve, said slide valve being urged by the pressure of the thirdpump to a position to open said second channel and block said flrstchannel.

19. In combination, a propeller, a hydraulic pitch-changing motortherefor, a first source of fluid under pressure; aspeed-responsive-governor-actuated valve controlling the application ofsaid fluid to said motor, stops limiting the extent of movement of saidmotor under the influence of said fluid, a second source or fluid underpressure higher than said first fluid pressure, means leading fluid atsaid higher pressure to said governor actuated valve, manuallycontrolled means for moving said valve to direct said higher fluidpressure to one side of said motor to render the limit stops ineflectiveand feather said propeller, said valve moving means comprising mechanismfor directing fluid to one end of said valve for moving it.

20. In combination, a propeller, a hydraulic pitch-changing motortherefor, a first source of fluid under pressure, aspeed-responsive-gover-' nor-actuated valve controlling the applicationof said fluid to said motor, a. second source of fluid under pressure,means leading fluid from said second source to said governor-actuatedvalve, mechanism for directing fluid from said, second source to apiston operatively connected with one end of said governor-actuatedvalve to move said valve and render said governor ineffective to actuatesaid valve, said valve when moved by said piston directing fluid fromsaid second source to one side of said motor.

anism for directing fluid to said piston includes a solenoid operatedvalve.

23. A device as claimed in claim 20 including an electrically drivenpump for providing said second source of fluid under pressure, asolenoid operated'valve for directing fluid to said piston and a commonswitch for simultaneously connecting said electrically drivenpump andsaid solenoid with a source of electricity.

24. In combination, a propeller, a hydraulic double-actingpitch-changing motor therefor, a first source of fluid under pressure, aspeed-re sponsive-governor-actuated valve controlling the application ofsaid fluid to said motor, a second source of fluid under pressure, meansleading fluid from said second source to said governor actuated valve,manually controlled means for moving said valve to direct fluid fromsaid second source to either selected side of said motor to eitherfeather or unieather said propeller, said valve moving means comprisingmechanism for directing fluid from said second source to a pistonoperatively connected-with said valve for moving it in one direction.other means for moving said valve in the other direction. a 25. A deviceas claimed in claim 24 including a pump actuated by rotation of saidpropeller providing said first source of fluid under pressure and inwhich said second source or fluid under pressure is independent ofrotation of said propeller.

26.- A device as claimed in claim 24 in which the other means for movingthe governor actuated valve in the other direction includes mechanismfor compressing the governor spring to move the valve.

27. In combination, a double-acting fluid-actuated propeller pitchchanging motor, a source of fluid under pressure, a valve, speedresponsive means, including a speeder spring, actuating said valve toselectively direct said fluid under pressure to either side of saidmotor, a movable speeder spring abutment, manually controlled means forselecting the governor speed setting,

including means for moving said abutment to a predetermined position toset the governor at a low speed setting. a second manually controlledmeans for energizing a source of fluid at a higher pressure, conduitsleading said fluid at said higher pressure to said valve, and meanscontrolled by said first mentioned manually controlled meansforpermitting energization of aid source of fluid at said higherpressure by said second manually controlled means only when saidabutment is in substantially said predetermined Position. i a

- ERIE MARTIN.

Certificate of Correction Patent No. 2,402,065. June 11, 1946.

ERLE MARTIN It is hereby certified that errors appear in the printedspecification of the above numbered patent requirin correction asfollows:' Column 10, line 50, claim 7, strike out to; and column 11, hne7, claim 9, for controlling read controlled; and that the said LettersPatent should be read with these corrections therein that the same mayconform to the record of the case in the Patent Oflice.

Signed and sealed this 29th day of October, A. D. 1946.

LESLIE FRAZER,

First Am'stant Oom/mz'ssioner of Patents.

